1. Field of the Invention
The present invention generally relates to a method for robustly processing and transmitting a digital broadcasting transport stream (TS), digital broadcasting transmission and reception systems, and signal processing methods thereof. More particularly, the present invention relates to a method for robustly processing and transmitting a digital broadcasting transport stream (TS) to enhance reception performance of a terrestrial-wave digital television (DTV) broadcasting system in the U.S. in accordance with the Advanced Television System Committee (ATSC) vestigial sideband (VSB) scheme, through information exchange and mapping with respect to a dual transport stream (TS) which includes a normal stream and a turbo stream, and digital broadcasting transmission and reception systems.
2. Description of the Related Art
The Advanced Television System Committee (ATSC) vestigial sideband (VSB) system, which is a terrestrial-wave digital television (DTV) broadcasting system in the U.S., is a single-carrier system that transmits a field sync signal for each unit of 312 data segments. Therefore, reception performance of the ATSC VSB system is not good on weak channels, specifically, on a Doppler-fading channel.
FIG. 1 is a block diagram of a typical ATSC VSB system including a digital broadcasting transmitter and a digital broadcasting receiver. The digital broadcasting transmitter as shown in FIG. 1, is configured in accordance with the enhanced VSB (E-VSB) system proposed by Philips, and is constructed to generate and transmit a dual stream in which robust or turbo data is added to normal data of the existing ATSC VSB system.
As shown in FIG. 1, the digital broadcasting transmitter includes a randomizer 11 which randomizes the dual stream; a Reed-Solomon (RS) encoder 12 which is a concatenated coder type for adding a parity byte to the transport stream (TS) to correct error occurring due to the channel characteristics in the transmission; an interleaver 13 which interleaves the RS-encoded data in a predetermined pattern; and a trellis encoder 14 which trellis-encodes the interleaved data at ⅔ rate with respect to the interleaved data and maps to 8-level symbols. With this structure, the digital broadcasting transmitter performs error correction coding with respect to the dual stream.
The digital broadcasting transmitter includes a multiplexer 15 and a modulator 16. The multiplexer 15 inserts a field synchronization (sync) and a segment synchronization (sync) to the data which passed through the error correction coding, as shown in accordance with a data format shown in FIG. 2. The modulator 16 inserts a pilot tone by adding a predetermined direct current (DC) value to a data symbol having the inserted segment and field sync signals, performs the VSB modulation by the pulse shaping, up-converts modulated data to a signal of a radio-frequency (RF) channel band, and transmits an up-converted signal.
According to the dual stream scheme which transmits the normal data and the robust (turbo) data through a single channel, the normal data and the robust data is multiplexed (not shown) and fed to the randomizer 11. The input data is randomized at the randomizer 11, the randomized data is outer-coded at the RS encoder 12 which is an outer encoder, and the coded data is spread at the interleaver 13. The interleaved data is inner-coded by a unit of 12 symbols at the trellis encoder 14. After the inner-coded data is mapped to 8-level symbols, the field sync signal and the segment sync signal are inserted in the mapped data. Next, the data is VSB-modulated by inserting the pilot tone, converted to an RF signal, and transmitted.
Meanwhile, the digital broadcasting receiver as shown in FIG. 1, includes a tuner (not shown) which converts the RF signal received through the channel to a baseband signal; a demodulator 21 which performs the sync detection and demodulation with respect to the converted baseband signal; an equalizer 22 which compensates channel distortion occurring by multi-path (multiple transmission paths) with respect to the demodulated signal; a Viterbi decoder 23 which corrects error of the equalized signal and decodes the error-corrected signal to symbol data;, a deinterleaver 24 which rearranges the symbol data spread by the interleaver 13 of the digital broadcasting transmitter; a RS decoder 25 which corrects error; and a derandomizer 26 which outputs an MPEG-2 (Moving Picture Experts Group) transport stream (TS) by derandomizing the data corrected by the RS decoder 25.
Accordingly, the digital broadcasting receiver, as shown in FIG. 1, restores the original signal by down-converting the RF signal to the baseband signal in a reverse operation of the digital broadcasting transmitter, shown in FIG. 1, demodulating and equalizing the down-converted signal, and performing the channel decoding to obtain the original signal.
FIG. 2 shows an example VSB data frame of an ATSC VSB system, in which a segment sync signal and a field sync signal are inserted. As shown in FIG. 2, one frame consists of 2 fields, and one field consists of a field sync segment, which is the first segment, and 312 data segments. In the VSB data frame, one segment corresponds to one MPEG-2 packet, and one segment consists of a 4-symbol segment sync signal and 828 data symbols.
In FIG. 2, the sync signals, which are the segment sync signal and the field sync signal, are used for the synchronization and the equalization at the digital broadcasting receiver, as shown in FIG. 1. That is, the field sync signal and the segment sync signal are known to the digital broadcasting transmitter and the digital broadcasting receiver of the terrestrial-wave digital broadcasting system shown in FIG. 1, and used as reference signals when the digital broadcasting receiver performs equalization.
The U.S. terrestrial-wave digital broadcasting system as shown in FIG. 1, which is constructed to generate and transmit the dual stream by adding the robust (turbo) data to the normal data of the existing ATSC VSB system, transmits the existing normal data together with the robust (turbo) data.
However, the U.S. terrestrial-wave digital broadcasting system as shown in FIG. 1 can not improve the poor reception performance in multi-path channels according to the existing normal data stream transmission although the dual stream is transmitted with the added robust (turbo) data. That is, the U.S. terrestrial-wave digital broadcasting system is disadvantageous in that the reception performance is not improved at all according to the improved normal stream. Moreover, the turbo stream does not improve the reception performance greatly in the multi-path environment either.